Collector grid and Interconnect structures for photovoltaic arrays and modules

ABSTRACT

A interconnected arrangement of photovoltaic cells is readily and efficiently achieved by using a unique interconnecting strap. The strap comprises electrically conductive fingers which contact the top light incident surface of a first cell and extend to an interconnect region of the strap. The interconnect region may include through holes which allow electrical communication between top and bottom surfaces of the interconnect region. In one embodiment, the electrically conductive surface of the fingers is in electrical communication with an electrically conductive surface formed on the opposite side of the strap through the through holes of the interconnect region. The interconnection strap may comprise a laminating film to facilitate manufacture and assembly of the interconnected arrangement.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 13/385,207 filed Feb. 6, 2012 entitled Collector Grid andInterconnect Structures for Photovoltaic Arrays and Modules, which is aContinuation-in-Part of U.S. patent application Ser. No. 12/803,490filed Jun. 29, 2010 entitled Collector Grid and Interconnect Structuresfor Photovoltaic Arrays and Modules, and now U.S. Pat. No. 8,138,413,which is a Continuation-in-Part of U.S. patent application Ser. No.12/798,221 filed Mar. 31, 2010 entitled Collector Grid and InterconnectStructures for Photovoltaic Arrays and Modules, and now U.S. Pat. No.8,076,568, which is a Continuation-in-Part of U.S. patent applicationSer. No. 11/980,010 filed Oct. 29, 2007 entitled Collector Grid andInterconnect Structures for Photovoltaic Arrays and Modules, nowabandoned.

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 13/385,207 filed Feb. 6, 2012 entitled Collector Grid andInterconnect Structures for Photovoltaic Arrays and Modules, which alsois a Continuation-in-Part of U.S. patent application Ser. No. 13/317,117filed Oct. 11, 2011, entitled Collector Grid, Electrode Structures andInterconnect Structures for Photovoltaic Arrays and Methods ofManufacture, and now U.S. Pat. No. 8,222,513, which is aContinuation-in-Part of U.S. patent application Ser. No. 13/199,333filed Aug. 25, 2011, entitled Collector Grid, Electrode Structures andInterconnect Structures for Photovoltaic Arrays and Methods ofManufacture, and now U.S. Pat. No. 8,110,737, which is a Continuation ofU.S. patent application Ser. No. 12/290,896 filed Nov. 5, 2008, entitledCollector Grid, Electrode Structures and Interconnect Structures forPhotovoltaic Arrays and Methods of Manufacture, now abandoned, which isa Continuation-in-Part of U.S. patent application Ser. No. 11/824,047filed Jun. 30, 2007, entitled Collector Grid, Electrode Structures andInterconnect Structures for Photovoltaic Arrays and other OptoelectricDevices, now abandoned, which is a Continuation-in-Part of U.S.application Ser. No. 11/404,168 filed Apr. 13, 2006, entitled Substrateand Collector Grid Structures for Integrated Photovoltaic Arrays andProcess of Manufacture of Such Arrays andnow U.S. Pat. No. 7,635,810.

This application is a Continuation-in-Part of U.S. patent applicationSer. No. 13/385,207 filed Feb. 6, 2012 entitled Collector Grid andInterconnect Structures for Photovoltaic Arrays and Modules, which is aContinuation-in-Part of U.S. patent application Ser. No. 12/590,222filed Nov. 3, 2009 entitled Photovoltaic Power Farm Structure andInstallation, which is a Continuation-in-Part of U.S. patent applicationSer. No. 12/156,505 filed Jun. 2, 2008 entitled Photovoltaic Power FarmStructure and Installation, now abandoned.

This application also claims priority to U.S. Provisional PatentApplication No. 61/274,960 filed Aug. 24, 2009 entitled Identification,Isolation, and Repair of Shunts and Shorts in Photovoltaic Cells.

The instant application claims the benefit of priority from all of theabove applications.

BACKGROUND OF THE INVENTION

Photovoltaic cells have developed according to two distinct methods. Theinitial operational cells employed a matrix of single crystal siliconappropriately doped to produce a planar-n junction. An intrinsicelectric field established at the p-n junction produces a voltage bydirecting solar photon produced holes and free electrons in oppositedirections. Despite good conversion efficiencies and long termreliability, widespread energy collection using single-crystal siliconcells is thwarted by the exceptionally high cost of single crystalsilicon material and interconnection processing.

A second approach to produce photovoltaic cells is by depositing thinphotovoltaic semiconductor films on a supporting substrate. Materialrequirements are minimized and technologies can be proposed for massproduction. The thin film structures can be designed according to dopedhomojunction technology such as that involving silicon films, or canemploy heterojunction approaches such as those using CdTe orchalcopyrite materials. Despite significant improvements in individualcell conversion efficiencies for both single crystal and thin filmapproaches, photovoltaic energy collection has been generally restrictedto applications having low power requirements. One factor impedingdevelopment of bulk power systems is the problem of economicallycollecting the energy from an extensive collection surface. Photovoltaiccells can be described as high current, low voltage devices. Typicallyindividual cell voltage is less than one volt. The current component isa substantial characteristic of the power generated. Efficient energycollection from an expansive surface must minimize resistive lossesassociated with the high current characteristic. A way to minimizeresistive losses is to reduce the size of individual cells and connectthem in series. Thus, voltage is stepped through each cell while currentand associated resistive losses are minimized.

It is readily recognized that making effective, durable seriesconnections among multiple small cells can be laborious, difficult andexpensive. In order to approach economical mass production of seriesconnected arrays of individual cells, a number of factors must beconsidered in addition to the type of photovoltaic materials chosen.These include the substrate employed and the process envisioned. Sincethin films can be deposited over expansive areas, thin film technologiesoffer additional opportunities for mass production of interconnectedarrays compared to inherently small, discrete single crystal siliconcells. Thus a number of U.S. patents have issued proposing designs andprocesses to achieve series interconnections among the thin filmphotovoltaic cells. Many of these technologies comprise deposition ofphotovoltaic thin films on glass substrates followed by scribing to formsmaller area individual cells. Multiple steps then follow toelectrically connect the individual cells in series array. Examples ofthese proposed processes are presented in U.S. Pat. Nos. 4,443,651,4,724,011, and 4,769,086 to Swartz, Turner et al. and Tanner et al.respectively. While expanding the opportunities for mass production ofinterconnected cell arrays compared with single crystal siliconapproaches, glass substrates must inherently be processed on anindividual batch basis.

More recently, developers have explored depositing wide area films usingcontinuous roll-to-roll processing. This technology generally involvesdepositing thin films of photovoltaic material onto a continuouslymoving web. However, a challenge still remains regarding subdividing theexpansive films into individual cells followed by interconnecting into aseries connected array. For example, U.S. Pat. No. 4,965,655 to Grimmeret. al. and U.S. Pat. No. 4,697,041 to Okamiwa teach processes requiringexpensive laser scribing and interconnections achieved with laser heatstaking. In addition, these two references teach a substrate of thinvacuum deposited metal on films of relatively expensive polymers. Theelectrical resistance of thin vacuum metallized layers significantlylimits the active area of the individual interconnected cells.

It has become well known in the art that the efficiencies of certainpromising thin film photovoltaic junctions can be substantiallyincreased by high temperature treatments. These treatments involvetemperatures at which even the most heat resistant polymers suffer rapiddeterioration, thereby requiring either ceramic, glass, or metalsubstrates to support the thin film junctions. Use of a glass or ceramicsubstrates generally restricts one to batch processing and handlingdifficulty. Use of a metal foil as a substrate allows continuousroll-to-roll processing. However, despite the fact that use of a metalfoil allows high temperature processing in roll-to-roll fashion, thesubsequent interconnection of individual cells effectively in aninterconnected array has proven difficult, in part because the metalfoil substrate is electrically conducting.

U.S. Pat. No. 4,746,618 to Nath et al. teaches a design and process toachieve interconnected arrays using roll-to-roll processing of a metalweb substrate such as stainless steel. The process includes multipleoperations of cutting, selective deposition, and riveting. Theseoperations add considerably to the final interconnected array cost.

U.S. Pat. No. 5,385,848 to Grimmer teaches roll-to-roll methods toachieve integrated series connections of adjacent thin film photovoltaiccells supported on an electrically conductive metal substrate. Theprocess includes mechanical or chemical etch removal of a portion of thephotovoltaic semiconductor and transparent top electrode to expose aportion of the electrically conductive metal substrate. The exposedmetal serves as a contact area for interconnecting adjacent cells. Thesematerial removal techniques are troublesome for a number of reasons.First, many of the chemical elements involved in the best photovoltaicsemiconductors are expensive and environmentally unfriendly. Thisremoval subsequent to controlled deposition involves containment, dustand dirt collection and disposal, and possible cell contamination. Thisis not only wasteful but considerably adds to expense. Secondly, theremoval processes are difficult to control dimensionally. Thus asignificant amount of the valuable photovoltaic semiconductor is lost tothe removal process. Ultimate module efficiencies are furthercompromised in that the spacing between adjacent cells grows, therebyreducing the effective active collector area for a given module area.

Thus there remains a need for an inexpensive manufacturing process whichallows high heat treatment for thin film photovoltaic junctions whilealso offering unique means to achieve effective integrated seriesconnections.

A further unsolved problem which has thwarted production of expansivesurface photovoltaic modules is that of collecting the photogeneratedcurrent from the top, light incident surface. Transparent conductiveoxide (TCO) layers have been employed as a top surface electrode.However, these TCO layers are relatively resistive compared to puremetals. This fact forces individual cell widths to be reduced in orderto prevent unacceptable resistive power losses. As cell widths decrease,the width of the area between individual cells (interconnect area)should also decrease so that the relative portion of inactive surface ofthe interconnect area does not become excessive. Typical cell widths ofone centimeter are often taught in the art. These small cell widthsdemand very fine interconnect area widths, which dictate delicate andsensitive techniques to be used to electrically connect the top TCOsurface of one cell to the bottom electrode of an adjacent seriesconnected cell. Furthermore, achieving good stable ohmic contact to theTCO cell surface has proven difficult, especially when one employs thosesensitive techniques available when using the TCO only as the topcollector electrode. The problem of collecting photovoltaic generatedcurrent from the top light impinging surface of a photovoltaic cell hasbeen addressed in a number of ways, none entirely successful.

In a somewhat removed segment of technology, a number of electricallyconductive fillers have been used to produce electrically conductivepolymeric materials. This technology generally involves mixing of theconductive filler into the polymer resin prior to fabrication of thematerial into its final shape. Conductive fillers typically consist ofhigh aspect ratio particles such as metal fibers, metal flakes, orhighly structured carbon blacks, with the choice based on a number ofcost/performance considerations. Electrically conductive resins havebeen used as bulk thermoplastic compositions, or formulated into paints.Their development has been spurred in large part by electromagneticradiation shielding and static discharge requirements for plasticcomponents used in the electronics industry. Other known applicationsinclude resistive heating fibers and battery components.

In yet another separate technological segment, electroplating on plasticsubstrates has been employed to achieve decorative effects on items suchas knobs, cosmetic closures, faucets, and automotive trim. ABS(acrylonitrile-butadiene-styrene) plastic dominates as the substrate ofchoice for most applications because of a blend of mechanical andprocess properties and ability to be uniformly etched. The overallplating process comprises many steps. First, the plastic substrate ischemically etched to microscopically roughen the surface. This isfollowed by depositing an initial metal layer by chemical reduction(typically referred to as “electroless plating”). This initial metallayer is normally copper or nickel of thickness typically one-halfmicrometer. The object is then electroplated with metals such as brightnickel and chromium to achieve the desired thickness and decorativeeffects. The process is very sensitive to processing variables used tofabricate the plastic substrate, limiting applications to carefullymolded parts and designs. In addition, the many steps employing harshchemicals make the process intrinsically costly and environmentallydifficult. Finally, the sensitivity of ABS plastic to liquidhydrocarbons has prevented certain applications. The conventionaltechnology for electroplating on plastic (etching, chemical reduction,electroplating) has been extensively documented and discussed in thepublic and commercial literature. See, for example, Saubestre,Transactions of the Institute of Metal Finishing, 1969, Vol. 47., orArcilesi et al., Products Finishing, March 1984.

A number of attempts have been made to simplify the electroplating ofplastics. If successful such efforts could result in significant costreductions for electroplated plastics and could allow facile continuouselectroplating of plastics to be practically employed, thus permittingnew applications. Some simplification attempts involve special chemicaltechniques, other that conventional electroless metal deposition, toproduce an electrically conductive film on the surface. Typical examplesof the approach are taught by U.S. Pat. No. 3,523,875 to Minklei, U.S.Pat. No. 3,682,786 to Brown et al., and U.S. Pat. No. 3,619,382 toLupinski. The electrically conductive surface film produced was intendedto be electroplated. Multiple performance problems thwarted theseattempts.

Other approaches contemplate making the plastic surface itselfconductive enough to allow it to be electroplated directly therebyavoiding the “electroless plating” or lamination processes. Efforts havebeen made to advance systems contemplating metal electrodepositiondirectly onto the surface of polymers made conductive throughincorporating conductive fillers. When considering polymers renderedelectrically conductive by loading with electrically conductive fillers,it may be important to distinguish between “microscopic resistivity” and“bulk” or macroscopic resistivity”. “Microscopic resistivity” refers toa characteristic of a polymer/filler mix considered at a relativelysmall linear dimension of for example 1 micrometer or less. “Bulk” or“macroscopic resistivity” refers to a characteristic determined overlarger linear dimensions. To illustrate the difference between“microscopic” and “bulk, macroscopic” resistivities, one can consider apolymer loaded with conductive fibers at a fiber loading of 10 weightpercent. Such a material might show a low “bulk, macroscopic”resistivity when the measurement is made over a relatively largedistance. However, because of fiber separation (holes) such a compositemight not exhibit consistent “microscopic” resistivity. When producingan electrically conductive polymer intended to be electroplated oneshould consider “microscopic resistivity” in order to achieve uniform,“hole free” deposit coverage. Thus, it may be advantageous to considerconductive fillers comprising those that are relatively small, but withloadings sufficient to supply the required conductive contacting. Suchfillers include metal powders and flake, metal coated mica or spheres,conductive carbon black, conductive nanoparticle materials, subdividedconductive polymers and the like.

Efforts to produce electrically conductive polymers suitable for directelectroplating have encountered a number of obstacles. The first is thecombination of fabrication difficulty and material propertydeterioration brought about by the heavy filler loadings often required.A second is the high cost of many conductive fillers employed such assilver flake.

Another obstacle involved in the electroplating of electricallyconductive polymers is a consideration of adhesion between theelectrodeposited metal and polymeric substrate (petal/polymer adhesion).In some cases such as electroforming, where the electrodeposited metalis eventually removed from the substrate, metal/polymer adhesion mayactually be detrimental. However, in most cases sufficient adhesion isrequired to prevent metal/polymer separation during extendedenvironmental and use cycles.

A number of methods to enhance adhesion have been employed. For example,etching of the surface prior to plating can be considered. Etching canoften be achieved by immersion in vigorous solutions such aschromic/sulfuric acid. Alternatively, or in addition, an etchablespecies can be incorporated into the conductive polymeric compound. Theetchable species at exposed surfaces is removed by immersion in anetchant prior to electroplating. Oxidizing surface treatments can alsobe considered to improve metal/plastic adhesion. These include processessuch as flame or plasma treatments or immersion in oxidizing acids.

In the case of conductive polymers containing finely divided metal, onecan propose achieving direct metal-to-metal adhesion betweenelectrodeposit and filler. However, here the metal particles aregenerally encapsulated by the resin binder, often resulting in a resinrich “skin”. To overcome this effect, one could propose methods toremove the “skin”, exposing active metal filler to bond to subsequentlyelectrodeposited metal.

Another approach to impart adhesion between conductive resin substratesand electrodeposits is incorporation of an “adhesion promoter” at thesurface of the electrically conductive resin substrate. This approachwas taught by Chien et al. in U.S. Pat. No. 4,278,510 where maleicanhydride modified propylene polymers were taught as an adhesionpromoter. Luch, in U.S. Pat. No. 3,865,699 taught that certain sulfurbearing chemicals could function to improve adhesion of initiallyelectrodeposited Group VIII metals.

An additional major obstacle confronting development of electricallyconductive polymeric resin compositions capable of being directlyelectroplated is the initial “bridge” of electrodeposit on the surfaceof the electrically conductive resin. In electrodeposition, thesubstrate to be plated is often made cathodic through a pressure contactto a metal contact tip, itself under cathodic potential. However, if thecontact resistance is excessive or the substrate is insufficientlyconductive, the electrodeposit current favors the metal contact and theelectrodeposit may have difficulty bridging to the substrate. The“bridging” problem extends to substrates having low surface currentcarrying capacity such as vacuum metallized or electrolessly platedfilms. In some cases, “burning” or actual “deplating” of very thin metaldeposits can be experienced during the initial moments of “bridge”formation.

Moreover, a further problem is encountered even if specialized rackingor contacting successfully achieves electrodeposit bridging to thesubstrate. Many of the electrically conductive polymeric resins haveresistivities far higher than those of typical metal substrates. Also inmany cases, such as the electroplating of conductive ink patterns orthin metal films, the conductive material may be relatively thin. Theinitial conductive substrate can be relatively limited in the amount ofelectrodeposition current which it alone can convey. In these cases theinitial conductive substrate may not cover almost instantly withelectrodeposit as is typical with thicker metallic substrates. Ratherthe electrodeposit coverage may result from lateral growth over thesurface, with a significant portion of the electrodeposition current,including that associated with the lateral electrodeposit growth,passing through the previously electrodeposited metal. This restrictsthe size and “growth length” of the substrate conductive pattern,increases plating costs, and can also result in large non-uniformitiesin electrodeposit integrity and thickness over the pattern.

Rates of this lateral growth likely depend on the ability of thesubstrate to convey current. Thus, the thickness and resistivity of theinitial conductive substrate can be defining factors in the ability toachieve satisfactory electrodeposit coverage rates. When dealing withextended electroplated patterns, long narrow metal traces are oftendesired, deposited on relatively thin initial conductive substrates suchas printed inks. These factors of course work against achieving thedesired result.

This coverage rate problem likely can be characterized by a continuum,being dependent on many factors such as the nature of the initiallyelectrodeposited metal, applied voltage, electroplating bath chemistry,the nature of the polymeric binder and the resistivity of theelectrically conductive polymeric substrate. As a “rule of thumb”, theinstant inventor estimates that coverage rate problems would demandattention if the resistivity of the conductive polymeric substrate roseabove about 0.001 ohm·cm. Alternatively, electrical current carryingcapacity of thin films is often reported as a surface resistivity in“ohms per square”. Using this measure, the inventor estimates thatcoverage rate issues may demand attention should the surface resistivityrise above about 0.01 ohms per square.

Beset with the problems of achieving adhesion and satisfactoryelectrodeposit coverage rates, investigators have attempted to producedirectly electroplateable polymers by heavily loading polymers withrelatively small conductive filler particles. Fillers include finelydivided metal powders and flake, conductive metal oxides andintrinsically conductive polymers. Heavy loadings may be sufficient toreduce both microscopic and macroscopic resistivity to levels where thecoverage rate phenomenon may be manageable. However, attempts to make anacceptable directly electroplateable resin using the relatively smallfillers alone encounter a number of barriers. First, the fine conductivefillers can be relatively expensive. The loadings required to achievethe particle-to-particle proximity to achieve acceptable conductivityincreases the cost of the polymer/filler blend dramatically. The finefillers may bring further problems. They tend to cause deterioration ofthe mechanical properties and processing characteristics of many resins.This significantly limits options in resin selection. All polymerprocessing is best achieved by formulating resins with processingcharacteristics specifically tailored to the specific process (injectionmolding, extrusion, blow molding printing, etc.). A required heavyloading of filler severely restricts ability to manipulate processingproperties in this way. A further problem is that metal fillers can beabrasive to processing machinery and may require specialized screws,barrels, and the like. Finally, despite being electrically conductive, apolymer filled with conductive particles still offers no mechanism toproduce adhesion of an electrodeposit since the particles may beessentially encapsulated by the resin binder, often resulting in anon-conductive or non-binding resin-rich “skin”.

For the above reasons, fine conductive particle containing plastics havenot been widely used as bulk substrates for directly electroplateablearticles. Rather, they have found applications in production ofconductive adhesives, pastes, and inks. Recent activity has beenreported wherein polymer inks heavily loaded with silver particles havebeen proposed as a “seed layer” upon which subsequent electrodepositionof metal is achieved. However, high material costs, applicationcomplexity, electrodeposit growth rate issues and adhesion remain withthese approaches. In addition, it has been reported that these films aretypically deposited at a thickness of approximately 3 microns resultingin a surface resistance of approximately 0.15 ohms per square. Such lowcurrent carrying capacity films likely would experience theelectroplating problems discussed above.

The least expensive (and least conductive) of the readily availableconductive fillers for plastics are carbon blacks. Typically theresistivity of a conductive polymer is not reduced below approximately 1ohm-cm using carbon black alone. Thus in a thin film form at a thicknessof 5 microns a surface resistivity would typically be approximately2,000 ohms per square. Attempts have been made to produce electricallyconductive polymers based on carbon black loading intended to besubsequently electroplated. Examples of this approach are the teachingsof U.S. Pat. Nos. 4,038,042, 3,865,699, and 4,278,510 to Adelman, Luch,and Chien et al. respectively.

Adelman taught incorporation of conductive carbon black into a polymericmatrix to achieve electrical conductivity required for electroplating.The substrate was pre-etched in chromic/sulfuric acid to achieveadhesion of the subsequently electroplated metal. However, the rates ofelectrodeposit coverage reported by Adelman may be insufficient for manyapplications.

Luch in U.S. Pat. No. 3,865,699 and Chien et al. in U.S. Pat. No.4,278,510 also chose carbon black as a filler to provide an electricallyconductive surface for the polymeric compounds to be electroplated. TheLuch U.S. Pat. No. 3,865,699 and the Chien U.S. Pat. No. 4,278,510 arehereby incorporated in their entirety by his reference. However, theseinventors further taught inclusion of an electrodeposit coverage orgrowth rate accelerator to overcome the galvanic bridging and lateralelectrodeposit growth rate problems described above. An electrodepositcoverage rate accelerator is an additive functioning to increase theelectrodeposition coverage rate over and above any affect it may have onthe conductivity of an electrically conductive polymer. In theembodiments, examples and teachings of U.S. Pat. Nos. 3,865,699 and4,278,510, it was shown that certain sulfur bearing materials, includingelemental sulfur, can function as electrodeposit coverage or growth rateaccelerators to overcome those problems associated with electricallyconductive polymeric substrates having relatively high resistivity.

In addition to elemental sulfur, sulfur in the form of sulfur donorssuch as sulfur chloride, 2 mercapto-benzothiazole,N-cyclohexyle-2-benzothiaozole sulfonomide, dibutyl xanthogen disulfide,and tetramethyl thiuram disulfide or combinations of these and sulfurwere identified. Those skilled in the art will recognize that thesesulfur donors are the materials which have been used or have beenproposed for use as vulcanizing agents or accelerators. Since thepolymer-based compositions taught by Luch and Chien et al. could beelectroplated directly they could be accurately defined as directlyelectroplateable resins (DER). These DER materials can be generallydescribed as electrically conductive polymers characterized by having anelectrically conductive surface with the inclusion of an electrodepositcoverage rate accelerator. In the following, the acronym “DER” will beused to designate a directly electroplateable resin as defined in thisspecification.

Specifically for the present invention, directly electroplateableresins, (DER), are characterized by the following features.

-   -   (a) presence of an electrically conductive polymer characterized        by having an electrically conductive surface;    -   (b) presence of an electrodeposit coverage rate accelerator;    -   (c) presence of the electrically conductive polymer        characterized by having an electrically conductive surface and        the electrodeposit coverage rate accelerator in the directly        electroplateable composition in cooperative amounts required to        achieve direct coverage of the composition with an        electrodeposited metal or metal-based alloy.

In his patents, Luch specifically identified elastomers such as naturalrubber, polychloroprene, butyl rubber, chlorinated butyl rubber,polybutadiene rubber, acrylonitrile-butadiene rubber, styrene-butadienerubber etc. as suitable for the matrix polymer of a directlyelectroplateable resin. Other polymers identified by Luch as usefulincluded polyvinyls, polyolefins, polysyrenes, polyamides, polyestersand polyurethanes.

In his patents, Luch identified carbon black as a means to render apolymer and its surface electrically conductive. As is known in the art,other conductive fillers can be used to impart conductivity to apolymer. These include metallic flakes or powders such as thosecomprising nickel or silver. Other fillers such as metal coated mineralsand certain metal oxides may also suffice. Furthermore, one might expectthat compositions comprising intrinsically conductive polymers may besuitable.

Regarding electrodeposit coverage rate accelerators, both Luch and Chienet al. in the above discussed U.S. patents demonstrated that sulfur andother sulfur bearing materials such as sulfur donor and acceleratorsserved this purpose when using an initial Group VIII “strike” layer. Onemight expect that other elements of Group 6A nonmetals, such as oxygen,selenium and tellurium, could function in a way similar to sulfur. Inaddition, other combinations of electrodeposited metals and nonmetalcoverage rate accelerators may be identified. Finally, theelectrodeposit coverage rate accelerator may not necessarily be adiscrete material entity. For example, the coverage rate accelerator mayconsist of a functional species appended to the polymeric binder chainor a species adsorbed onto the surface of the conductive filler. It isimportant to recognize that such an electrodeposit coverage rateaccelerator can be extremely important in order to achieve directelectrodeposition in a practical way onto polymeric substrates havinglow conductivity or very thin electrically conductive polymericsubstrates having restricted current carrying ability.

As pointed out above in this specification, attempts to dramaticallysimplify the process of electroplating on plastics have met withcommercial difficulties. Nevertheless, the current inventor haspersisted in personal efforts to overcome certain performancedeficiencies associated with electroplating onto material structureshaving low current carrying ability, conductive plastics and DER's.Along with these efforts has come a recognition of unique and eminentlysuitable applications for electrically conductive polymers and oftenmore specifically de DER technology. Some examples of these uniqueapplications for electroplated items include solar cell electricalcurrent collection grids and interconnect structures, electricalcircuits, electrical traces, circuit boards, antennas, capacitors,induction heaters, connectors, switches, resistors, inductors,batteries, fuel cells, coils, signal lines, power lines, radiationreflectors, coolers, diodes, transistors, piezoelectric elements,photovoltaic cells, emi shields, biosensors and sensors. One readilyrecognizes that the demand for such functional applications forelectroplated articles is relatively recent and has been particularlyexplosive during the past decade.

Regarding the DER technology, a first recognition is that the“microscopic” material resistivity generally is not reduced below about1 ohm-cm. by using conductive carbon black alone. This is several ordersof magnitude larger than typical metal resistivities. Other well knownfinely divided conductive fillers (such as metal flake or powder, metalcoated minerals, graphite, or other forms of conductive carbon) can beconsidered in DER applications requiring lower “microscopic”resistivity. In these cases the more highly conductive fillers can beconsidered to augment or even replace the conductive carbon black.

Moreover, the “bulk, macroscopic” resistivity of conductive carbon blackfilled polymers can be further reduced by augmenting the carbon blackfiller with additional highly conductive, high aspect ratio fillers suchas metal containing fibers. This can be an important consideration inthe success of certain applications such as achieving higher currentcarrying capacity for a buss. Furthermore, one should realize thatincorporation of non-conductive fillers may increase the “bulk,macroscopic” resistivity of conductive polymers loaded with finelydivided conductive fillers without significantly altering the“microscopic resistivity” of the conductive polymer. This is animportant recognition regarding DER's in that electrodeposit coveragespeed depends on the presence of an electrodeposit coverage rateaccelerator and on the “microscopic resistivity” and less so on the“macroscopic resistivity” of the DER formulation. Thus, large additionalloadings of functional non-conductive fillers can be tolerated in DERformulations without undue sacrifice in electrodeposit coverage rates oradhesion. These additional non-conductive loadings do not greatly affectthe “microscopic resistivity” associated with the polymer/conductivefiller/electrodeposit coverage rate accelerator “matrix” since thenon-conductive filler is essentially encapsulated by “matrix” material.Conventional “electroless” plating technology does not permit thiscompositional flexibility.

Yet another recognition regarding the DER technology is its ability toemploy polymer resins and formulations generally chosen in recognitionof the fabrication process envisioned and the intended end userequirements. In order to provide clarity, examples of some suchfabrication processes are presented immediately below in subparagraphs 1through 6.

-   -   (1) Should it be desired to electroplate an ink, paint, coating,        or paste which may be printed or formed on a substrate, a good        film forming polymer, for example a soluble resin such as an        elastomer, can be chosen to fabricate a DER ink (paint, coating,        paste etc.). The DER ink composition can be tailored for a        specific process such flexographic printing, rotary silk        screening, gravure printing, flow coating, spraying etc.        Furthermore, additives can be employed to improve the adhesion        of the DER ink to various substrates. One example would be        tackifiers.    -   (2) Should it be desired to electroplate a fabric, a DER ink can        be used to coat all or a portion of the fabric intended to be        electroplated. Furthermore, since DER's can be fabricated out of        the thermoplastic materials commonly used to create fabrics, the        fabric itself could completely or partially comprise a DER. This        would eliminate the need to coat the fabric.    -   (3) Should one desire to electroplate a thermoformed article or        structure, DER's would represent an eminently suitable material        choice. DER's can be easily formulated using olefinic materials        which are often a preferred material for the thermoforming        process. Furthermore, DER's can be easily and inexpensively        extruded into the sheet like structure necessary for the        thermoforming process.    -   (4) Should one desire to electroplate an extruded article or        structure, for example a sheet or film, DER's can be formulated        to possess the necessary melt strength advantageous for the        extrusion process.    -   (5) Should one desire to injection mold an article or structure        having thin walls, broad surface areas etc. a DER composition        comprising a high flow polymer can be chosen.    -   (6) Should one desire to vary adhesion between an        electrodeposited DER structure supported by a substrate the DER        material can be formulated to supply the required adhesive        characteristics to the substrate. For example, the polymer        chosen to fabricate a DER ink can be chosen to cooperate with an        “ink adhesion promoting” surface treatment such as a material        primer or corona treatment. In this regard, it has been observed        that it may be advantageous to limit such adhesion promoting        treatments to a single side of the substrate. Treatment of both        sides of the substrate in a roll to roll process may adversely        affect the surface of the DER material and may lead to        deterioration in plateability. For example, it has been observed        that primers on both sides of a roll of PET film have adversely        affected plateability of DER inks printed on the PET. It is        believed that this is due to primer being transferred to the        surface of the DER ink when the PET is rolled up.

All polymer fabrication processes require specific resin processingcharacteristics for success. The ability to “custom formulate” DER's tocomply with these changing processing and end use requirements whilestill allowing facile, quality electroplating is a significant factor inthe teachings of the current invention. Conventional plasticelectroplating technology does not permit great flexibility to “customformulate”.

Another important recognition regarding the suitability of DER's for theteachings of the current invention is the simplicity of theelectroplating process. Unlike many conventional electroplated plastics,DER's do not require a significant number of process steps during themanufacturing process. This allows for simplified manufacturing andimproved process control. It also reduces the risk of crosscontamination such as solution drag out from one process bath beingtransported to another process bath. The simplified manufacturingprocess will also result in reduced manufacturing costs.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is the ability they offer to selectively electroplatean article or structure. As will be shown in later embodiments, it isoften desired to electroplate a polymer or polymer-based structure in aselective manner. DER's are eminently suitable for such selectiveelectroplating.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is their ability to withstand the pre-treatments oftenrequired to prepare other materials for plating. For example, were a DERto be combined with a metal, the DER material would be resistant to manyof the pre treatments such as cleaning which may be necessary toelectroplate the metal.

Yet another recognition of the benefit of DER's for the teachings of thecurrent invention is that the desired plated structure often requiresthe plating of long and/or broad surface areas. As discussed previously,the coverage rate accelerators included in DER formulations allow forsuch extended surfaces to be covered in a relatively rapid manner thusallowing one to consider the use of electroplating of conductivepolymers.

These and other attributes of DER's in the practice of the instantinvention will become clear through the following remainingspecification, accompanying figures and claims.

In order to eliminate ambiguity in terminology, for the presentinvention the following definitions are supplied:

“Metal-based” refers to a material or structure having at least onemetallic property and comprising one or more components at least one ofwhich is a metal or metal-containing alloy.

“Alloy” refers to a substance composed of two or more intimately mixedmaterials.

“Group VIII metal-based” refers to a substance containing by weight 50%to 100% metal from Group VIII of the Periodic Table of Elements.

“Electroplateable material” refers to a material that exhibits a surfacethat can be exposed to an electroplating process to cause the surface tocover with electrodeposited material.

OBJECTS OF THE INVENTION

An object of the invention is to eliminate the deficiencies in the priorart methods of producing expansive area, series interconnectedphotovoltaic arrays.

A further object of the present invention is to provide improvedprocesses whereby expansive area, interconnected photovoltaic arrays canbe economically mass produced.

A further object of the invention is to provide improved processes andstructures for supplying current collector grids and interconnectionstructures.

Other objects and advantages will become apparent in light of thefollowing description taken in conjunction with the drawings andembodiments.

SUMMARY OF THE INVENTION

The current invention provides a solution to the stated need byproducing the active photovoltaic film and interconnecting structureseparately and subsequently combining them to produce the desiredexpansive interconnected array.

In one embodiment, the interconnect structure is laminated to the lightincident surface of a photovoltaic cell. If desired the separatelyprepared interconnection structure allows the photovoltaic junction tobe produced in bulk. Furthermore, the junction can be produced with awide variety of photovoltaic materials including but not limited to,single crystal silicon, polycrystalline silicon, amorphous silicon, CIS,CIGS, cadmium telluride, copper sulfide, semiconductor inks, polymerbased semiconductor inks etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a structure forming a starting article foran embodiment of the invention.

FIG. 1A is a top plan view of another embodiment of a starting articleof the invention.

FIG. 2 is a sectional view taken substantially from the perspective oflines 2-2 of FIG. 1.

FIG. 2A is a sectional view taken substantially from the perspective oflines 2A-2A of FIG. 1A.

FIG. 2B is a sectional view showing a possible structure of the articleof FIGS. 1 and 2 in more detail.

FIG. 3 is a sectional view showing another embodiment of the basicstructure depicted in FIG. 2.

FIG. 4 is a top plan view showing the initial article depicted in FIG. 1following an additional processing step.

FIG. 5 is a sectional view taken substantially from the perspective oflines 5-5 of FIG. 4.

FIG. 6 is an exploded sectional view of the encircled region of FIG. 5identified as 6-6.

FIG. 7 is a sectional view of the article of FIGS. 4 through 6, takenfrom a similar perspective of FIG. 5, showing the FIGS. 4 through 6embodiment following an additional optional processing step.

FIG. 8 is an exploded sectional view of the encircled region of FIG. 7identified as 8-8.

FIG. 9 is a top plan view of a photovoltaic cell useful in the practiceof the invention.

FIG. 10 is a sectional view taken substantially from the perspective oflines 10-10 of FIG. 9.

FIG. 11 is an exploded sectional view showing the detail of thestructure identified as layers 70 and 86 in FIG. 10.

FIG. 12 is a simplified depiction of one form of process possible in themanufacture of the article embodied in FIGS. 9 and 10.

FIG. 13 is a sectional view showing one embodiment of an arrangementappropriate to combine the articles of FIG. 7 with the article of FIGS.9 and 10 to achieve a series interconnected photovoltaic assembly.

DESCRIPTION OF PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals designate identicalor corresponding parts throughout several views and an additional letterdesignation is characteristic of a particular embodiment.

Referring now to FIGS. 1 through 3, there are shown embodiments of astarting structure for a grid/interconnect article of the invention.FIG. 1 is a top plan view of a polymeric film or glass article generallyidentified by numeral 10. Article 10 has width X-10 and length Y-10.Length Y-10 is sometimes much greater the width X-10 such that article10 can be processed in essentially a “roll-to-roll” fashion. However,this is not necessarily the case. Dimension “Y” can be chosen accordingto the application and process envisioned. FIG. 2 is a sectional viewtaken substantially from the perspective of lines 22 of FIG. 1.Thickness dimension Z-10 is normally small in comparison to dimensionsY-10 and X-10 and thus article 10 has a sheetlike structure. Article 10is further characterized by having regions of essentially solidstructure combined with regions having holes 12 extending through thethickness Z-10. In the FIG. 1 embodiment, a substantially solid regionis generally defined by a width Wc, representing a current collectionregion. The region with through-holes (holey region) is generallydefined by width Wi, representing an interconnection region. Imaginaryline 11 separates the two regions. The reason for these distinctions anddefinitions will become clear in light of the following teachings.

FIGS. 1A and 2A is another embodiment of a sheetlike structure similarto that embodied in FIGS. 1 and 2 but absent the through holes presentin the interconnection region Wi of the embodiment of FIGS. 1 and 2.

The instant invention will be taught using the structure embodied inFIGS. 1 and 2. However, one skilled in the art will readily recognizeapplication of the teachings to the structure embodied in FIGS. 1A and2A and other equivalent structures when appropriate.

Referring now to FIG. 2, article 10 has a first surface 20 and secondsurface 22. The sectional view of article 10 shown in FIG. 2 shows asingle layer structure. This depiction is suitable for simplicity andclarity of presentation. Often, however, article 10 will be a laminatecomprising multiple layers as depicted in FIG. 2B. In the FIG. 2Bembodiment, article 10 is seen to comprise multiple layers 14, 16, 18,etc. The multiple layers may comprise inorganic or organic componentssuch as thermoplastics, thermosets, or silicon containing glass-likelayers. The various layers are intended to supply functional attributessuch as environmental barrier protection or adhesive characteristics.Such functional layering is well known and widely practiced in theplastic food packaging art. In particular, in light of the teachings tofollow, one will recognize that it may be advantageous to have layer 14forming surface 20 comprise a sealing material such as an ethylene vinylacetate (EVA) containing material for adhesive characteristics during apossible subsequent lamination process. For example, the invention hasbeen successfully demonstrated using a standard laminating material soldby GBC Corp., Northbrook, Ill., 60062. Additional layers 16, 18 etc. maycomprise materials which assist in support or processing such aspolypropylene and polyethylene terepthalate and barrier materials suchas fluorinated polymers.

As depicted in the embodiments of FIGS. 1 and 2, the solid regions Wcand “holey” regions Wi of article 10 comprise the same material. This isnot necessarily the case. For example, the “holey” regions Wi of article10 could comprise a fabric, woven or non-woven, joined to an adjacentsubstantially solid region along imaginary line 11. However, thematerials forming the solid region should be relatively transparent ortranslucent to visible light, as will be understood in light of theteachings to follow.

FIG. 3 depicts an embodiment wherein multiple widths 10-1, 10-2 etc. ofthe general structure of FIGS. 1 and 2 are joined together in agenerally repetitive pattern in the width direction. As will becomeclear by the following teachings, such a structure may be advantageousin certain applications of photovoltaic cell interconnection.

FIG. 4 is a plan view of the FIG. 1 structure 10 following an additionalprocessing step, and FIG. 5 is a sectional view taken along line 5-5 ofFIG. 4. In FIGS. 4 and 5, the article is now designated by the numeral24 to reflect this additional processing. In FIGS. 4 and 5, it is seenthat a pattern of “fingers” 26 has been formed by material 28 positionedin a pattern onto surface 20 of original article 10. “Fingers” 26 extendover the width Wc of the solid sheetlike structure 24. The “fingers” 26extend to the “holey” interconnection region generally defined by Wi.Portions of the Wc region not overlayed by “fingers” 26 remaintransparent or translucent to visible light. The “fingers” may compriseelectrically conductive material. Examples of such materials are metalcontaining inks, patterned deposited metals such as etched metalpatterns, intrinsically conductive polymers and DER formulations. The“fingers” may comprise materials intended to facilitate subsequentdeposition of conductive material in the pattern defined by the fingers.An example of such a material would be ABS, which can be catalyzed toinitiate chemical “electroless” metal deposition. In a preferredembodiment, the “fingers” comprise material which will enhance or allowsubsequent metal electrodeposition such as a DER. In the embodiment ofFIGS. 4 and 5, the “fingers” are shown to be a single layer forsimplicity of presentation. However, the “fingers” can comprise multiplelayers of differing materials chosen to support various functionalattributes.

Continuing reference to FIGS. 4 and 5 also shows additional material 30applied to the “holey” region Wi of article 24. As with the materialcomprising the “fingers” 26, the material 30 applied to the “holey”region Wi is either conductive or material intended to promotesubsequent deposition of conductive material. In the embodiment of FIGS.4 and 5, the “holey” region takes the general form of a “buss” 31extending in the Y-24 direction in communication with the individualfingers. However, as one will understand through the subsequentteachings, the invention requires only that conductive communicationextend from the fingers to a region Wi intended to be electricallyjoined to the electrode of an adjacent cell. The “holey” region Wi thusdoes not require overall electrical continuity in the “Y” direction asis characteristic of a “buss” depicted in FIGS. 4 and 5.

Reference to FIG. 5 shows that the material 30 applied to the “holey”interconnection region Wi is shown as the same as that applied to formthe fingers 26. However, these materials 28 and 30 need not beidentical. In this embodiment material 30 applied to the “holey” regionextends through holes 12 and onto the opposite second surface 22 ofarticle 24. This is best seen in FIG. 6, which is an exploded view ofthe portion of article 24 encircled by circle 6-6 of FIG. 5. Theextension of material 30 through the holes 12 can be readilyaccomplished as a result of the relatively small thickness (Z dimension)of the sheetlike article. Techniques include two sided printing ofconductive inks, through hole deposition of chemically (electroless)deposited metal, through hole deposition of conductive inks andconductive polymers, and through hole electrodeposition.

FIG. 7 is a view similar to that of FIG. 5 following an additionaloptional processing step. FIG. 8 is an exploded view of the portion ofFIG. 7 encircled there as 8-8. The article embodied in FIGS. 7 and 8 isdesignated by numeral 36 to reflect this additional processing. It isseen in FIGS. 7 and 8 that the additional processing has depositedhighly conductive material 32 over the originally free surfaces ofmaterials 28 and 30. Material 32 is normally metal-based such as copperor nickel, tin etc. Typical deposition techniques such as chemical orelectrochemical metal deposition can be used for this additionaloptional process to produce the article 36. In a preferred embodiment,electrodeposition is chosen for its speed, ease, and cost effectiveness.

It is seen in FIGS. 7 and 8 that highly conductive material 32 extendsthrough holes to electrically join and form electrically conductivesurfaces on opposite sides of article 36. While shown as a single layerin the FIG. 7 and FIG. 8 embodiment, the highly conductive material cancomprise multiple layers to achieve functional value. In particular, alayer of copper is often desirable for its high conductivity. Nickel isoften desired for its adhesion characteristics, plateability andcorrosion resistance. The exposed surface 39 of material 32 can beselected for corrosion resistance and bonding ability. In particular,tin or tin containing alloys are a possible choice of material to formthe exposed surface of material 32. Tin and tin containing alloys meltat relatively low temperature, which may be desirable to promote ohmicjoining to other components in subsequent processing such as lamination.

The structures and articles such as those embodied in FIGS. 4 though 8are defined herein as forms of “interconnecting straps” or simply“straps”.

Referring now to FIGS. 9 and 10, there is embodied a thin filmphotovoltaic cell generally identified by the numeral 40. Cell 40 has alight incident top surface 59 and a bottom surface 66. Cell 40 has awidth X-40 and length Y-40. Width X-40 defines a first photovoltaic cellterminal edge 45 and second photovoltaic cell terminal edge 46. In somecases, particularly during initial cell manufacture, dimension Y-40 maybe considerably greater than dimension X-40 such that cell 40 cangenerally be described as “continuous” or being able to be processed ina roll-to-roll fashion. However, this “continuous” characteristic is nota requirement for the instant invention. FIG. 10 shows that cell 40comprises a thin film semiconductor structure 70 supported onmetal-based foil 72. Foil 72 has a first surface 74, second surface 76,and thickness Z-40. Metal-based foil 72 may be of uniform composition ormay comprise a laminate of two or more metal-based layers. For example,foil 72 may comprise a base layer of inexpensive and processablematerial 78 with an additional metal-based layer 81 disposed betweenbase layer 78 and semiconductor material 70. The additional metal-basedlayer may be chosen to ensure good ohmic contact between the top surface74 of foil 72 and semiconductor structure 70. Bottom surface 76 of foil72 may comprise a material 79 chosen to achieve good electrical andmechanical joining characteristics as will become clear in thesubsequent teachings. The thickness Z-40 is often chosen such that cell40 remains flexible for roll-to-roll handling and to minimize weight.However, the invention is not limited to flexible, lightweight cells andthe teachings contained herein can be applied to rigid cells such asthose comprising glass substrates or superstrates or those comprisingsingle crystal silicon cells.

Semiconductor structure 70 can be any of the photovoltaic structuresknown in the art. Included are cells comprising single crystal silicon,polycrystalline silicon, thin film cells such as those comprising CuS,CIS, CIGS and CdTe, and cells comprising polymer based semiconductors.In its simplest form, a photovoltaic cell combines an n-typesemiconductor with a p-type semiconductor to form an n-p junction. Mostoften an optically transparent window electrode, identified as 86 inFIG. 10, such as a thin film of zinc or tin oxide is employed tominimize resistive losses involved in current collection. FIG. 11illustrates an example of a typical photovoltaic cell structure insection. In the figures, an arrow labeled “hv” is used to indicate thelight incident side of the structure. In FIG. 11, 80 represents a thinfilm of a p-type semiconductor, 82 a thin film of n-type semiconductorand 84 the resulting photovoltaic junction. Window electrode 86completes the typical photovoltaic structure.

FIG. 12 presents one method of manufacture of a foil supportedphotovoltaic structure such as embodied in FIGS. 9 and 10. Themetal-based foil 72 is moved in the direction of its length Y through adeposition process, generally indicated by numeral 90. Process 90accomplishes deposition of the active photovoltaic structure onto foil72. Foil 72 is unwound from supply roll 92, passed through depositionprocess 90 and rewound onto take up roll 94. Process 90 can comprise anyof the processes well-known in the art for depositing thin filmphotovoltaic structures. These processes include electroplating, vacuumsputtering, and chemical deposition. Process 90 may also includetreatments, such as heat treatments or slitting, intended to enhanceperformance or manufacturing ability.

One method of combining the interconnect “straps” embodied in FIGS. 4-6and optionally in FIGS. 7 and 8 with the photovoltaic cells embodied inFIGS. 9 and 10 is illustrated in FIG. 13. In the FIG. 13 structure,individual straps 36 a, 36 b, 36 c, are combined with cells 40 a, 40 b,40 c to form a series interconnected array. This may be accomplished viathe following process.

-   -   1. An individual strap, such as 36 a, is combined with a cell        such as 40 a by positioning the free surface 20 of solid surface        region We of strap 36 a in registration with the light incident        surface 59 of cell 40 a. Adhesion joining the two surfaces is        accomplished by a suitable process. It is envisioned that batch        or continuous laminating processing, such as that widely used in        the food packaging industry would be one suitable method to        accomplish this surface joining. In particular, the material        forming the remaining free surface 20 of article 36 a (that        portion of surface 20 not covered with conductive material 32)        can be chosen to promote good adhesion between the sheetlike        article 36 a and cell 40 a during a surface laminating process.        Also, as mentioned above, the nature of the free surface of        conductive material 32 may be manipulated and chosen to further        guarantee ohmic joining and adhesion. The laminating process        brings the conductive material of fingers 26 into firm and        effective contact with the transparent conductive material 86        forming surface 59 of cell 40 a.    -   2. Subsequently or concurrently with Step 1, the conductive        material 32 extending over the second surface 22 of strap 36 b        is ohmicly adhered to the bottom surface 66 of cell 40 a. This        joining accomplished by suitable electrical joining techniques        such as soldering, riveting, spot welding or conductive adhesive        application. The particular ohmic joining technique is not shown        in the FIG. 13. However, a particularly suitable conductive        adhesive is one based on a carbon black filler in a polymer        matrix. Such adhesive formulations are relatively inexpensive.        Despite the fact that carbon black formulations have relatively        high intrinsic resistivities (of the order 1 ohm·cm.), the        bonding in this embodiment is accomplished through a relatively        thin adhesive layer and over a broad surface. Thus the resulting        resistance losses are relatively limited. Strap 36 b extends        over the light incident surface of cell 40 b.

FIG. 13 embodies three cells assembled in a series arrangement using theteachings of the instant invention. In FIG. 13, “i” indicated thedirection of net current flow. It is noted that the arrangement of FIG.13 resembles a shingling arrangement of cells, but with an importantdistinction. The prior art shingling arrangements have included anoverlapping of cells at a sacrifice of portions of very valuable cellsurface. In the FIG. 13 teaching, the benefits of the shinglinginterconnection concept are achieved without any loss of photovoltaicsurface from shading by an overlapping cell. In addition, the FIG. 13arrangement retains a high degree of flexibility because there is noimmediate overlap of the metal foil structure.

Example

A standard plastic laminating sheet from GBC Corp. was coated with DERin the pattern of repetitive fingers joined along one end with abusslike structure resulting in an article as embodied in FIGS. 1A and2A. The fingers were 0.020 inch wide, 1.625 inch long and wererepetitively separated by 0.150 inch. The buss-like structure whichcontacted the fingers extended in a direction perpendicular to thefingers as shown in FIG. 2A. The buss-like structure had a width Wi of0.25 inch. Both the finger pattern and buss-like structure were printedsimultaneously using the same DER ink and using silk screen printing.The DER printing pattern was applied to the laminating sheet surfaceformed by the sealing layer (i.e. that surface facing to the inside ofthe standard sealing pouch).

The finger/buss pattern thus produced on the lamination sheet was thenelectroplated with nickel in a standard Watts nickel bath at a currentdensity of 50 amps. per sq. ft. Approximately 4 micrometers of nickelthickness was deposited to the overall pattern.

A photovoltaic cell having surface dimensions of 1.75 inch wide by2.0625 inch long was used. This cell was a CIGS semiconductor typedeposited on a 0.001 inch stainless steel substrate. A section of thelaminating sheet containing the electroplated buss/finger pattern wasthen applied to the top, light incident side of the cell, with theelectroplated grid finger extending in the width direction (1.75 inchdimension) of the cell. Care was taken to ensure that the buss orinterconnect region, Wi, of the electroplated laminate did not overlapthe cell surface. This resulted in a total cell surface of 3.61 sq.inch. (2.0625″×1.75″) with about 12% shading from the grid, (i.e. about88% open area for the cell).

The electroplated “finger/buss” on the lamination film was applied tothe photovoltaic cell using a standard Xerox office laminator. Theresulting completed cell showed good appearance and connection.

The cell prepared as above was tested in direct sunlight fixphotovoltaic response. Testing was done at noon, Morgan Hill, Calif. onApril 8 in full sunlight. The cell recorded an open circuit voltage of0.52 Volts. Also recorded was a “short circuit” current of 0.65 Amp.This indicates excellent power collection from the cell at highefficiency of collection.

Although the present invention has been described in conjunction withpreferred embodiments, it is to be understood that modifications,alternatives and equivalents may be included without departing from thespirit and scope of the inventions, as those skilled in the art willreadily understand. Such modifications, alternatives and equivalents areconsidered to be within the purview and scope of the invention andappended claims.

1. An article comprising a combination of a first photovoltaic cell andan interconnection component, said first photovoltaic cell comprisingsemiconductor material and having top surface formed by a windowelectrode comprising a transparent or translucent first conductivematerial, said top cell surface facing upward toward a source of light,said interconnection component being flexible and further comprising asubstrate having a sheetlike form such that said substrate has athickness small in comparison to its length and width, said substratecomprising one or more polymeric layers and further having a downwardfacing bottom side and an upward facing top side, said interconnectioncomponent further characterized as having a collection region and aninterconnection structure, said collection region comprising atransparent or translucent portion of said substrate wherein thedownward facing bottom side is formed by one or more of said polymericlayers, said collection region further comprising a second conductivematerial in the form of a coating, said coating overlaying a basematerial, said second conductive material not including any of saidfirst conductive material forming said top surface of said firstphotovoltaic cell, said interconnection structure comprising additionalelectrically conductive material extending from said bottom side to saidtop side of said substrate, and further extending over a portion of saidtop side, said additional conductive material being in ohmic electricalcommunication with said second electrically conductive material, saidcombination having said portion of said substrate associated with saidcollection region overlaying a preponderance of said light incident topsurface of said first photovoltaic cell such that a portion of saidsecond electrically conductive material is in direct physical contactwith said window electrode forming said light incident top surface ofsaid first photovoltaic cell.
 2. The article of claim 1 wherein saidwindow electrode forming said cell top surface comprises a transparentconductive metal oxide
 3. The article of claim 1 wherein said firstphotovoltaic cell is a thin film CIGS cell.
 4. The article of claim 1wherein portions of said second electrically conductive material andsaid additional electrically conductive material comprise a monolithicmaterial common to both portions.
 5. The article of claim 4 wherein saidmonolithic material comprises a continuous metal.
 6. The article ofclaim 1 wherein at least a portion of said bottom side of said substrateassociated with said collection region is formed by an adhesivematerial.
 7. The article of claim 6 wherein a portion of said secondconductive material is positioned between said adhesive material andsaid top cell surface.
 8. The article of claim 1 wherein a continuouslayer of adhesive material forms substantially the entirety of thebottom substrate side overlaying said top surface of said photovoltaiccell and portions of said adhesive layer are adhesively bonded to saidtop cell surface.
 9. The article of claim 8 wherein said polymericadhesive is a laminating adhesive.
 10. The article of claim 1 whereinsaid article has a length much greater than width whereby said articlecan be characterized as continuous in length.
 11. The article of claim 1wherein said article is flexible.
 12. The article of claim 1 whereinsaid second conductive material forms multiple substantially parallelline segments.
 13. The article of claim 12 wherein two or more of saidparallel line segments comprise a common monolithic material.
 14. Thearticle of claim 12 wherein said second conductive material comprises amonolithic material layer common to all of said substantially parallelline segments.
 15. The article of claim 1 wherein said second conductivematerial comprises nickel.
 16. The article of claim 1 wherein saidportion of said second conductive material in contact with said windowelectrode is absent polymeric material.
 17. The article of claim 1wherein said second conductive material comprises an electricallyconductive polymer.
 18. The article of claim 1 wherein said photovoltaiccell comprises a self supporting metal based foil and wherein saidsemiconductor material covers the full expanse of an upward facingsurface of said metal based foil.
 19. The article of claim 1 furthercomprising, a second photovoltaic cell, said second cell having anelectrically conductive bottom surface portion facing away from a lightincident top surface and formed by a metal-based foil, and said secondcell being positioned such that said conductive bottom surface portionof said second cell overlays at least a portion of said interconnectionstructure, and wherein said portion of said second conductive materialin direct physical contact with said top window electrode of said firstphotovoltaic cell and at least a portion of said additional electricallyconductive material extending over said second side of said substratecomprise a monolithic material common to both portions, and wherein saidmonolithic material is in ohmic contact with said electricallyconductive bottom surface of said second cell.
 20. The article of claim19 wherein both said first and second cells have terminal edges definedby the extent of said semiconductor material, said first and secondcells being interconnected in series, and wherein said article iscapable of achieving series connection without requiring eitheroverlapping of said cells or substantial separation of adjacent terminaledges of said cells in a direction parallel to said light incidentsurfaces.
 21. The article of claim 1 wherein said electricalcommunication between said additional conductive material extending oversaid second side and said second conductive material is established byconductive material extending through one or more holes in saidsubstrate from the downward facing substrate side to the upward facingsubstrate side.
 22. The article of claim 1 wherein said secondelectrically conductive material has a melting point below that of tin.23. The article of claim 12 wherein a connecting conductive materialextends between an endpoint of a first of said parallel line segments toan endpoint of a second of said parallel line segments and wherein saidconnecting conductive material and portions of said first and secondparallel line segments comprise a common continuous monolithic metalform.